The present invention relates to a reservoir tank, and in particular to a cap of a reservoir tank.
In general, a conventional reservoir tank to be used in association with a brake master cylinder which is disclosed for example in Japanese Patent Laid open Print No.63(1988)-145158 is set to store an amount of operating fluid to be used in the brake master cylinder. During vehicle's travel, the vibration as a result thereof is transmitted to the reservoir tank, thereby generating the waving of the surface of the operating fluid. Since a cap for closing an opening of a tank body is Provided with a passage which is set to establish an air communication between an inner space of the tank body and the atmosphere, the resultant waving fluid is subject to leak through the passage. In light of this phenomena, in a conventional reservoir tank, a deflector is formed at a lower portion of the cap and a diaphragm is disposed between the cap and the deflector in order to prevent the waving fluid from reaching the cap.
However, in the foregoing improved structure, a slit is formed in the diaphragm and a hole is formed in the deflector for maintaining the inner space of the reservoir tank at the atmospheric pressure, resulting in that the fear of the leakage of the operating fluid through the hole and the slit.